1. Field of the Invention
The present invention relates to a portable storage medium with a magnetic stripe such as a multifunctional IC card with a magnetic stripe.
2. Description of the Prior Art
A multifunctional IC card houses an IC chip comprising a CPU and a memory, a liquid crystal display (hereafter LCD) and a thin battery packaged on a wiring board in a portable-sized card body. The display unit of the LCD can be seen from outside through a suitably opened window, and a keyboard is provided on the surface of the card body. Also, contacts are formed on the surface of the card body for sending/receiving required data to and from external systems, such as a reader/writer.
According to ISO (International Organisation for Standardisation) standard, the thickness of a multifunctional IC card is defined as 0.76 mm, and the length and width are also respectively defined as prescribed dimensions.
A multifunctional IC card has not only a recording function for required information, but also various functions such as key input, calculation, and character display. Therefore, in order to strengthen rigidity and to protect the housed electronic components against external impact and load, the multifunctional IC card requires high rigidity. As shown in FIGS. 1 and 2, a card body 10 of the multifunctional IC card was constructed as a metal case in which a pair of stainless steel outer plates 12 and 14 were bonded by welding to a stainless steel outer frame 16. A contact section 18 composed of a plurality of contacts is formed on stainless steel outer plate 12 and a wiring board 20 is located between the pair of stainless steel outer plates 12 and 14.
From the viewpoint of combined use with the magnetic cards as, for example, cash cards for banks, the present multifunctional IC cards are constructed as hybrid multifunctional IC cards. On the hybrid multifunctional IC card, a magnetic stripe 22 is bonded onto the surface of the card body 10 for magnetically recording information in a similar way to magnetic cards.
On the other hand, a magnetic stripe reader in the automatic cash dispenser systems provided by banks are constructed for use with a magnetic stripe bonded on to a card body which has flexibility because it is made of resin.
In a conventional multifunctional IC card with a magnetic stripe, a magnetic stripe 22 was bonded onto the surface of the stainless steel outer plate 12, which has high rigidity. Therefore, magnetic stripe 22 did not adapt itself readily to the magnetic heads MH in the magnetic stripe readers which are in general use, as shown in FIG. 3. Therefore, there were cases of incorrect reading and writing of information.
Also, since card body 10 was composed of a metal case in which a pair of stainless steel outer plates 12 and 14 were bonded to outer frame 16 by welding, there were cases of distortion occurring in outer plates 12 and 14 during welding. This resulted in wave-like deformation of the surfaces, and also caused wave-like deformation of the surface of the magnetic stripe bonded to such outer plate. Since a magnetic stripe with such a wave-like deformation often does not make correct contact with magnetic head MH, there is a problem in that randomness occurs in the magnetic output, and further difficulty is caused in the correct reading and writing of magnetic information.
Further, in a conventional multifunctional IC card with a magnetic stripe, metal with a permeability greater than 1.005 is used to form the stainless steel outer plates 12 and 14. However, since stainless steel outer plates 12 and 14 have a permeability of more than 1.005, information data often cannot be written accurately on magnetic stripe 12. That is, as shown in FIG. 4, magnetic head MH makes contact with magnetic stripe 22 the information data is being written on magnetic stripe 22 formed on outer plate 12. Magnetic flux generated by magnetic head MH, as shown by dotted lines, not only passes through the layer of magnetic stripe 22, but also passes through the layer of outer plate 12 due to a leak magnetic flux from magnetic stripe 22. Therefore, since the magnetic flux cannot pass sufficiently through magnetic stripe 22, it is difficult to obtain good magnetic recording on magnetic stripe 22. As a result, an accurate reading of the information data from magnetic stripe 22 is very difficult due to small level of output of the magnetic flux from the stripe 22 in comparison to the plate 12.